Bifocal lens



L. W. BUGBEE.

BIFOCAL LENS.

(APPLICATION FILED MAY 28,1921.

1,427,577Q I PELt6I1t6dAl 1g-29, 1922.

INVEN TOR. Lac/4N 14/. 506865.

A TTORNEY:

LUGZCAN W. EBUQB'EE, @111 INDIANAZGEEEQ INDIANA.

BIE OGAL il'iEl l'S.

To all whom c'tmao concern:

Be it known that I, Lnomn W. Eocene, o. citizen of the United States, and o resident of lndienopolis', county of Marion, and State oi lndiena, have invented it certein new and useful Bifocal Lens; and i do hereby declare that the following is e full, clear, and erect description thereof; reference being had to the eccompenyin drawings, in which like numerals refer to 11 e ports.

This invention relates to on improved bifocal lens of the Kryptok type, wherein the minor portion or insert is secured to the major portion of the lens by e gloss or like cementing material which has n lower melting point either the crown or the flint gloss. By gloss cement, or cementing glass or like cementing materiel, referred to herein is meant we cementing material formed of glass or other vitreous materiel.

.Lenses of this type heretofore have consisted of e major portion for distance mode of crown glass or glass having e relatively low index of refroction,'and having e recess in one side thereof, leaving a concave spherically disposed surface in which an insert of flint gloss or class having it high index of refraction. hes oeen secured to constitute the reading portion of the lens. The two kinds of glass hove been secured to gether heretofore by fusing them together or cementing the some together with enedien balsam or like cement,

In the drawings, Figure 1 is o plenyiew oi a Kryptolr lens blank in eccordencewith this invention, t e contour-oi the finished lens being indicated by a dotted line. Fig. 2 is a control vertical section of Fig. l, but on an enlarged scale.

Fig. 3 is a section of s portion of Fig. 2 on an enlarged 'scele.

In the drowings there is shown the main or distence portion 10 of e lens blank, which portion is usually made of crown gloss, and o reading portion -11 which is usually mode of flint glass, soid reading portion 11 being cemented to the major or distance portion 10 by on intermediate layer of glass cement or the like 12,

In carrying out my present invention, the some process is employed es heretofore exce oting that e gloss cement is employed for securing the flint or reading gloss insert to the crown glass or major portion of the lens, end when the lens is completed, said cement Specification of Letters Patent. 7 yat mt fil A 29 11921; fieriol No. 273,346.

'gless is in the form of a, thin layer between the flint and crown gloss portions.

The cementing glass, if used simply as a bond to secure the flint and crown glass together when they have substantially similarcurvatures, one convex and the otherv concove, will be very thin with theoreticelly parallel surfaces and without any refractive power to affect the power of that. portion of the lens. By making the concave depression in the major lens of a stronger curvature than the convex surifece of the flint added portion as shown in hig. 3, and using cementing glass as above explained for securing them together, which is of a higher inderi oi retireetion then either the flint or crown glass, the layer of cementing glass will have the sheet of a positive meniscus lens.

The cementing glass may be colorless or it may be colored in such e way as to ebsorb a. predetermined portion of the visible spectrum. Thus the cementing gloss nieybe of such nature as to absorb light from one end of the visible spectrum while the added or flint portion of the glass may be oi such a nature as to ebsorb light from the opposite end of the spectrum, All three of the kinds of-gless employed, namely, the crown glass,

the flint glass and the cementing gloss, I

have different properties as regards light absorption and each selectively absorbs a predetermined part of the spectrum, as desired.

Another advantage or" this invention is that such e lens may lmlllfl-(lfiB with both the major portion end the minor or reading portion of glass or a low index of refrection, like crown gloss, preferably herd crown capable of resisting scratches end the I cementing gloss be such as to furnish the necessary higher index of. refraction for the reading portion the lens In making this invention, the cementing glass referred to of lower melting point than either the crown or ordinary flint gloss, may be lead borote. But if both the mejor and minor segments be crown gloss, then any flint gloss may be used as e cementing glass for all flint glass has a lower melting point thencrown gloss. v

.l. em swore that it hes been common prectice to make Kryptok lenses or the like by using balsam, es heretofore stated, and that balsam hes a lower melting point then the pieces of glass cemented together by it; but I am not aware of any lens of this type having been made wherein the cementing material was made of glass or other vitreous material, whereby the two pieces of glass are permanently secured together or have the other characteristics above referred to. The balsam is not a permanent cement and it does not lend to the lens the characteristics herein referred to. The-cement formed of glass or other vitreous material is'hard and in its various characteristics closely approaches the crown and flint glass which is secured together by the cement, and the pieces of glass and the glass cement are in ,eflect welded together so as to make a more perfect and more nearly homogeneous lens and one as nearly integral-as any lens could be formed of more than one piece of glass or when the two portions of the lens are fused together, and yet have-the other characteristics and advantages herein. set forth. The glass or vitreous cement has a lower melting point than the major and minor portions of the lens so that when the crown. and lint glass portions are being cemented together, neitherof them will be melted or otherwise altered or affected, as is'the casewhen they are fused together. The fusion in this inventionis limited to the glass cement and hence the crownand flint glass portions are not injured or destroyed during the uniting process, as is so frequently the case when they are being fused together,

The invention claimed is:

1. A bifocal lens formed of two pieces of glass, and a glass cement securing said pieces of lass 'to each other which has a lower melting oint than said pieces of-glass.

2. A bifoca lens consisting or a major portion or: glass with a recess in one side thereof, a'minor portion of glass fitting in said recess, and a cementing glass in said recess having a lower melting point than either of said portionsof glass for securing them together. 1

an bifocal lens consisting of a major portion of glass of a relatively low index of refraction having a recess in one side thereof, a minor portion of glass of a relatively high index of refraction in said recess, and cementing glass in said recess having a lower melting point than either of said portions of glass for securing-them together.

i. A bifocal lens consisting of a major portion of crown glass having a recess in one side thereof, a minor portion of flint glass fitting. in said recess, and cementing glass in said recess having a lower melting point than either of said portions of glass :t'or securing them together.

5. A bifocal. lens having amajor pori tion with a spherically disposed concave surface in one side thereof, a minor portion having a spherically-disposed convex surface of weaker curvaturethan the curvature vof said recessed surface in the major portion of the lens, and cementing glass in said recess for securing the two portions of glass to each other;

A bifocal lens consisting of a major portion formed of glass capable of absorbing one part of the visible spectrum with a recess in one side thereof, a minor portion in said recess formed of glass capable of absorbing another portion ofthe visible spectrum, and a cementing glass in said recess for securing said two portions of glass together, said cementing glass ca able of absorbing still another portion or the'visihle spectrum.

in witness whereof, I have hereunto at fixed my signature.

LUCIAN N. BUGBEE. 

